Peripheral neuropathy

Peripheral Neuritis, Polyneuropathy

What is Peripheral neuropathy?

Peripheral neuropathy is nerve damage that affects the peripheral nervous system (PNS). It can cause symptoms such as pain, loss of sensation or inability to control muscles. In practical usage, the term “peripheral neuropathy” is used interchangeably with the term “neuropathy,” which indicates any type of nerve damage. Peripheral neuropathy is very common. As many as 20 million Americans have neuropathy, according to The Neuropathy Association.

The nervous system controls virtually all activity in the body, including breathing, thinking and movement. It is divided into two parts. The brain and spinal cord make up the central nervous system (CNS), which processes information from the senses and responds with commands to the muscles and glands in the body. The second part of the nervous system is called the peripheral nervous system. The PNS includes the autonomic nervous system (ANS), which is not under a person's conscious control.

The nerves of the PNS are divided into three categories:

Autonomic nerves. Regulates activities in the body that are not under a person's conscious control. Examples include breathing, digesting food, and functions of the heart and glands.

Motor nerves. Transmits information from the brain and spinal cord to the rest of the body. These nerves control movements of all muscles under conscious control. This includes grasping things, talking and walking.

Sensory nerves. Transmits information about sensory experiences such as the sensation of feeling someone's touch or the pain that results from a cut.

The nerves of the PNS relay information from the brain and spinal cord (the CNS) to various points in the body. In addition, the PNS relays information from the body back to the CNS. For example, the PNS may send sensory information back to the CNS indicating that a person's feet are cold, which would then trigger a response from the CNS to take steps to warm the feet. Damage to PNS nerves can short-circuit these messages, preventing them from being sent at all or causing them to be sent at the wrong time or too slowly.

Peripheral neuropathy may occur as a result of damage to a single nerve (mononeuropathy) but is more likely to include multiple nerves (polyneuropathy). In some cases, two or more isolated nerves in separate areas of the body may be affected (mononeuritis multiplex).

Peripheral neuropathy causes various levels of discomfort depending on which nerves are affected and the extent of damage to the nerves. The most common symptoms of peripheral neuropathy are weakness, numbness, tingling and pain, which can be mild to severe. Because motor and sensory axons run in the same nerve bundle, damage to a specific nerve bundle typically affects both motor and sensory functions.

Neuropathies are rarely life-threatening unless other diseases are complicating factors.

Types and differences of peripheral neuropathy

More than 100 types of peripheral neuropathy have been identified. Each has its own symptoms and prognosis, which are dependent on the type of nerves affected – autonomic, motor or sensory.

Peripheral neuropathies are generally classified as being acute or chronic. Acute neuropathies involve symptoms that appear suddenly, that progress rapidly and that subside slowly as the nerves begin to heal. In contrast, chronic neuropathies feature symptoms that emerge subtly and unfold gradually over time. People with chronic neuropathies may see their symptoms progress, or may experience discomfort that eventually plateaus. In other cases, symptoms may go into remission, only to re-emerge in the future.

Types of peripheral neuropathies include:

Diabetic neuropathy

Neuropathy that occurs as a result of damaged caused by high levels of blood sugar. Diabetes experts have identified four types of diabetic neuropathy – autonomic, focal, peripheral and proximal. However, it is important to note that many experts consider all of these neuropathies as belonging to the category of peripheral neuropathy.

Autonomic neuropathy

Autonomic neuropathy is a collection of symptoms that occurs as a result of damage to the nerves of the autonomic nervous system (ANS). The ANS regulates involuntary functions of the body such as heart rate, blood pressure, digestion and perspiration. Patients with autonomic neuropathy experience discomfort (e.g., bladder and bowel dysfunction, gastrointestinal problems) but the condition is rarely life-threatening.

Proximal neuropathy

Nerve damage that can affect the legs, thighs, hips and buttocks – usually on just one side of the body. It causes weakness and pain that usually requires treatment. People with type 2 diabetes have an increased risk of this type of neuropathy.

Neuropathy secondary to drugs

Damage to the nerves resulting from the toxic effect of using certain medications. Examples include heart and blood pressure medications, anticonvulsants, cholesterol drugs and others.

Alcoholic neuropathy

Decreased nerve function as a result of excessive alcohol consumption. Experts disagree about the cause of this form of neuropathy, but it may be a result of the toxic effect of alcohol on nerve tissue.

Guillain-Barré syndrome (GBS)

Condition in which the body's immune system attacks the nerves of the peripheral nervous system (PNS). Two-thirds of all patients with GBS reported having a recent bacterial or viral infection.

Charcot-Marie-Tooth disease

Group of hereditary disorders resulting in flaws in the genes that manufacture neurons or the myelin sheath. Symptoms include extreme weakening and wasting of muscles in the lower legs and feet, gait problems, loss of tendon reflexes, and lower-limb numbness.

Friedreich's ataxia

Inherited disease that causes progressive damage to the nervous system. The first symptom may be difficulty walking. Symptoms then spread to the arms and trunk and range from muscle weakness and speech problems to heart disease.

Trigeminal neuralgia

Also known as tic douloureux, it involves damage to the large nerve of the head and face. Symptoms include severe pain on one side of the face that has been described as “lightning-like.”

How is it diagnosed?

Signs and symptoms of Peripheral neuropathy

Symptoms depend on whether the neuropathy mainly affects sensory nerve fibers or motor nerve fibers. Damage to sensory nerve fibers may result in numbness and tingling.
Sensations of cold or pain, often starting in the hands and feet, spread toward the center of the body. Damage to motor fibers may result in muscle weakness and wasting.
Symptoms of autonomic nerve damage may include blurred vision, impaired or absent sweating, episodes of faintness associated with falling blood pressure, and disturbances in gastric, intestinal, bladder (incontinence), and sexual (impotence) functions.

Diagnosing peripheral neuropathy can be difficult, because symptoms can vary so much from person to person. In addition, it can be very difficult to determine exactly what type of neuropathy a patient has. A physician typically will compile a thorough medical history and perform a complete physical examination of the patient. In addition, a neurological examination is often performed.

Various tests may be performed to pinpoint the cause of a patient's peripheral neuropathy. For example, blood tests may reveal the presence of diabetes, liver or kidney dysfunction, or vitamin deficiencies. A spinal tap may be used to look for abnormal antibodies in a patient's cerebrospinal fluid that my indicate neuropathy. Imaging tests such as computed axial tomography (CAT scan) and magnetic resonance imaging (MRI) also may be helpful.

Other tests that may be performed include:

Nerve conduction velocity (NCV) tests. A nerve fiber is stimulated, which generates an electrical impulse. An electrode further down the nerve's pathway records the speed of impulse transmission. Abnormal results may indicate nerve damage.

Electromyography (EMG). A needle is inserted into a muscle to compare electrical activity in muscles at rest and during muscle contraction.

Nerve biopsy. Removes a sample of nerve tissue for analysis, most often from the lower leg.

A physician also may test a patient's muscle strength or ability to perceive touch, temperature and pain. Underlying conditions responsible for peripheral neuropathy may be revealed through additional testing for cardiovascular disease, connective tissue disorders and malignancies.

How is Peripheral neuropathy treated?

Acquired neuropathies (i.e., those that are not caused by inherited conditions) usually are best treated by addressing the underlying condition causing the nerve damage. In some cases, surgery may be helpful, such as when a nerve is compressed due to an entrapment injury. An examples of such a surgery is a carpal tunnel syndrome release. There is no cure for most inherited neuropathies.

If the condition itself cannot be cured, symptoms associated with peripheral neuropathy may be reduced or eliminated through various therapies. Over-the-counter analgesics can be used to treat mild neuropathies. Anticonvulsants, antidepressants and anesthetics also may be used.

Use of certain devices such as wheelchairs, hand or foot braces and splints can either help compensate for muscle weakness or alleviate nerve compression. In some cases, orthopedic shoes can help people with gait problems. Mechanical ventilation can aid the breathing of patients with severe forms of neuropathy.

As long as the nerve cell itself has not been destroyed, peripheral nerves have the ability to regenerate. This may be helped by physical therapy or occupational therapy. Physical therapy includes a mixture of exercises, massage and other treatments to maintain strength and flexibility. Occupational therapy is similar to physical therapy, but it focuses on improving patients' fine motor skills.

Other steps that can help a person relieve symptoms associated with neuropathies include:

Avoiding toxin exposure

Limiting alcohol consumption

Restoring proper vitamin levels

Quitting smoking

Maintaining good health is often the best defense against the damage of neuropathies. This includes maintaining a healthy weight, engaging in regular exercise and eating a well-balanced diet.

In addition, patients often are advised to take various measures to increase their safety, which may help prevent certain injuries that can cause peripheral neuropathy. Safety measures may include installing railings and adequate lighting and removing potentially dangerous obstacles (e.g., loose rugs). Patients are urged to avoid placing prolonged pressure on the body's pressure points, such as elbows and knees. Pressure in these areas can result in additional nerve damage.